diff --git a/src/assembler_arm.h b/src/assembler_arm.h
index bd5ed0b..f6be2b9 100644
--- a/src/assembler_arm.h
+++ b/src/assembler_arm.h
@@ -630,7 +630,7 @@
 // Slowpath entered when Thread::Current()->_exception is non-null
 class ArmExceptionSlowPath : public SlowPath {
  public:
-  ArmExceptionSlowPath(ArmManagedRegister scratch) : scratch_(scratch) {}
+  explicit ArmExceptionSlowPath(ArmManagedRegister scratch) : scratch_(scratch) {}
   virtual void Emit(Assembler *sp_asm);
  private:
   const ArmManagedRegister scratch_;